Mark Bridge writes:

Just a few weeks ago WiFi was made available on a number of London Underground stations - yet mobile coverage still stops when you go down the escalator.

So why is it taking so long for us to get mobile phone service on the Tube?

For an insight into some of the challenges and the possible solutions I spoke to Ian Brown, CEO of Axell Wireless. The company is a leader when it comes to providing additional wireless coverage in confined spaces - from tunnels to sports stadiums - and is currently involved in the project to install mobile phone service on the Channel Tunnel.

Extending mobile coverage inside a railway tunnel can be done in one of two ways. Either an existing signal from outside the site can be filtered, amplified and ‘rebroadcast’ in the tunnel using a Distributed Antenna System (DAS) or a direct connection with a mobile network base station can be arranged.

Although the London Underground system would be a challenging environment in which to install mobile phone coverage, Ian has no doubt that it’s possible. In fact, Axell Wireless has already helped install public safety wireless coverage across much of the London tube network.

“It is a well-trodden path”, he explained. “It is perfectly feasible. There are lots of design issues around metros, space is very limited, but certainly the technology absolutely exists.”

We went on to discuss some of the specific technical challenges facing engineers, including capacity issues, equipment design and the need to run a ‘radiating cable’ along each rail tunnel requiring coverage.

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